This is something I've been working on. I've been trying to break Yuriko, the Tiger's Shadow in legacy since the card came up. I've been testing it with Emrakul, the Aeons Torn nearly since it's release. (You can find my page on another page.) and recently, people have been toying with the same design. So this is what I've been working on.
Companion:
1 Obosh, the Preypiercer
Creatures:
4 Changeling Outcast
2 Emrakul, the Aeons Torn
4 Mothdust Changeling
3 Yuriko, the Tiger’s Shadow
Artifacts:
4 Retrofitter Foundry
Instant:
4 Brainstorm
2 Force of Negation
4 Force of Will
2 Swords to Plowshares
Sorcery:
2 Show and Tell
4 Ponder
Planeswalker:
2 Teferi, Time Raveler
I need to replace:
3 Baleful Strix
2 Ingenious Infiltrator
Due to them being even CMC.
Then there's lands, mine are pretty budget, I can't really afford Underground Sea. I've been mostly playing basics with lots of fetches.
One neat interaction between Yuriko, the Tiger’s Shadow, and Obosh, the Preypiercer is that not only does she deal 2 damage, instead of 1, her effect also is doubled. So if you top a FoW, you're hitting for 10. That also counts for all your other creatures getting hits as well. (I believe? I could be wrong. xD) Which makes most swings with Obosh, the Preypiercer out, dangerously lethal.

